The present invention is directed, in general, to a conditioning wheel for a semiconductor wafer polishing pad and, more specifically, to a conditioning wheel that has a retainer coating deposited over the abrasive particles that inhibit the abrasive particles from dislodging from a surface of the conditioning wheel during a conditioning process.
In the manufacture of the integrated circuits (ICs) derived from semiconductor wafers, chemical-mechanical planarization (CMP) is used to provide smooth topographies of the wafer substrates on which ICs are formed for subsequent lithography and material deposition.
Unfortunately, during the CMP process the polishing pad often collects particulate material from the slurry, as well as byproducts from the polishing process. Over time, this material begins to clog the pad, inhibiting the CMP process. When the pad becomes clogged, it becomes necessary to condition the pad in order to restore its original shape and properties. That is, the material must be removed before it completely clogs the pad and results in a surface that does not effectively polish the semiconductor wafer, or a surface that scratches or otherwise damages the wafer. In short, to properly polish a semiconductor wafer, the performance of the polishing pad should not be compromised.
In conventional processes, to condition the polishing pad, a conditioning wheel with a surface of diamond abrasives embedded in a nickel/stainless steel alloy setting is used. Referring initially to FIG. 1, illustrated is a polishing pad conditioning wheel 100 found in the prior art. The conditioning wheel 100 includes a planar body 110 and an upper surface 120, typically composed of metal or a metal alloy, for conditioning a semiconductor wafer polishing pad (not illustrated).
The upper surface 120 of the conditioning wheel 100 includes abrasive particles, one of which is designated 140, that are embedded in the upper surface 120. The abrasive particles 140 are typically diamond crystals. These diamond crystals are well suited for conditioning the polishing surface of a polishing pad, which must be done periodically to keep the polishing pad at optimum polishing efficiency.
As the conditioning wheel 100 is repeatedly used, its effectiveness at reconditioning the surface of a polishing pad decreases. Perhaps the most common reason for this decrease may be that the abrasive particles 140 become worn and rounded, losing their polishing effectiveness. However, a more pressing concern for this degradation may be that the abrasive particles 140 in the upper surface 120 become lose and fall out of the upper surface 120 of the conditioning wheel 100, as illustrated by arrow 150. Of course, this reduces the effective surface area of the conditioning wheel 100 and slows the conditioning process. Moreover, this condition becomes even more pressing if many abrasive particles 140 are lost from a single area of the upper surface 120. In such a case, the conditioning wheel 100 may begin to condition a polishing pad unevenly, which may translate into damaging or unevenly polishing a semiconductor wafer undergoing the CMP process. Once dislodged, the abrasive particles 140 that fall from the conditioning wheel 100 cannot be replaced with new particles. In time, when a substantial number of abrasive particles 140 have been lost, the capabilities of the conditioning wheel 100 are so lost that it must be replaced with a new one, usually at significant costs.
Perhaps more importantly, the loss of abrasive particles 140 during the conditioning process is not only undesirable from a cost standpoint, but also from a quality standpoint as the abrasive particles 140 can become embedded in the polishing pad just conditioned. Once embedded in the polishing pad, the abrasive particles 140 will easily scratch a semiconductor wafer undergoing CMP, in some cases damaging it beyond repair. With the high cost of semiconductor materials, manufacturers are understandably eager to avoid damaging, and thus, discarding wafers during the CMP process.
Accordingly, what is needed in the art is an improved conditioning wheel for conditioning a semiconductor wafer polishing pad that does not suffer from the deficiencies found in the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides an improved polishing pad conditioning wheel. In one embodiment, the conditioning wheel includes a planar body having a metal surface located thereon. The metal surface has abrasive particles embedded therein, and a retainer coating deposited over the metal surface and the abrasive particles. The retainer coating inhibits the abrasive particles from dislodging during a conditioning process. The retainer coating includes a wide range of coatings that would inhibit the abrasive particles from dislodging from the condition wheel.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the scope of the invention in its broadest form.